Arduino and a thermometer

Connect to a thermometer

Best and most common choice (for non highly demanding applications) is the LM35 from National (Panasonic electronic branch).
Feed the baby with anything between 0 and 35 V (!), you get a reading between -1 and %206V on the Vout pin (in basic mode, most likely what you need; see pdf for other possibilities).
Reading returns %200.01v per degree above 0. Convert to Celsius degrees like that :

val = analogRead(potPin);             //read the value of sensor
temperature = (5*val*100/1024);         //convert voltage to temperature

Documentation

Official documentation from National: LM35.pdf

Links

• Sample program on the Arduino forum http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1203159459